Desiccant air conditioners are attracting attention as future air conditioners, because, unlike cooling-based dehumidification systems, desiccant air conditioners cool the air after dehumidifying it and so do not cause the growth of mold and bacteria, and what is more, desiccant air conditioners do not use chlorofluorocarbons.
FIG. 7 shows the configuration of a commonly-used desiccant air conditioner “a”. That is to say, in the desiccant air conditioner “a”, an intake path “b” that passes air SA from outdoors to indoors and an exhaust path “c” that passes air RA from indoors to outdoors are provided adjacent to each other in a counterflow manner so that the airs SA and RA flow in opposite directions, and a desiccant rotor “d” and a sensible heat rotor “e” are provided such that these rotors straddle the intake path “b” and the exhaust path “c”. The air SA that has been taken into the intake path “b” from outdoors is dehumidified by the desiccant rotor “d” and then cooled by the sensible heat rotor “e” before being supplied indoors. On the other hand, the air RA that has been taken into the exhaust path “c” from indoors is heat-recovered by the sensible heat rotor “e”, then further heated by a heater “f”, and then absorbs moisture from the desiccant rotor “d” before being exhausted outdoors.
In this case, the desiccant rotor “d” is formed in a disk shape from a moisture absorbent material and thus has air permeability, and this rotor is provided perpendicular to the flows of the airs SA and RA in the intake path “b” and the exhaust path “c” and configured to rotate and come into contact alternately with the airs SA and RA passing through the intake path “b” and the exhaust path “c” to repeat sorption (moisture absorption) and desorption (moisture release). That is to say, although the desiccant rotor “d” absorbs moisture from the air SA passing through the intake path “b”, once the rotor “d” has rotated and thus moved to the exhaust path “c”, the rotor releases moisture into the air RA passing through this exhaust path “c” and is dried. As a result, the dehumidifying capacity of the rotor is regenerated. Then, the desiccant rotor “d” rotates again and thus moves to the intake path “b”. After that, the rotor repeats the same operation as described above over and over again.
In the desiccant air conditioner “a” as described above, the dehumidifying capacity depends on the performance of the desiccant rotor “d”, and therefore there has been a limitation to the ability to adjust humidity and temperature. In particular, since the desiccant rotor “d” generates heat of moisture absorption when absorbing moisture from the air SA passing through the intake path “b”, the moisture absorbing capacity decreases, and so there has also been a limitation to the ability to increase the dryness.
Thus, conventionally, in order to enhance the dehumidifying capacity, which depends on the desiccant rotor, there have been proposed desiccant air conditioners including a desiccant air conditioner that employs a desiccant rotor having two dehumidification regions through which the air in the intake path passes and one regeneration region through which the air in the exhaust path passes, as disclosed in Patent Document 1.
In this desiccant air conditioner, the air from the intake path is guided to the desiccant rotor and dehumidified in the first dehumidification region, then guided to a heat exchanger and cooled by heat exchange with the air from the exhaust path, then guided to the desiccant rotor and dehumidified in the second dehumidification region, then cooled by heat exchange with a low-temperature heat source of a heat pump, and afterward supplied indoors. Moreover, the air from the exhaust path is heated by heat exchange with the air from the intake path, then further heated by a heat source of the heat pump, and then guided to the desiccant rotor and heats the regeneration region to cause moisture retained by this regeneration region to be released, thereby regenerating the moisture absorbing capacity of the desiccant rotor.
Moreover, another example of the desiccant air conditioners that have been proposed is a desiccant air conditioner that employs a desiccant rotor having one dehumidification region through which the air in the intake path passes and two regeneration regions through which the air in the exhaust path passes, as disclosed in Patent Document 2.
In this desiccant air conditioner, the air from the intake path is guided to the desiccant rotor and dehumidified in the dehumidification region, then guided to a heat exchanger and cooled by heat exchange with the air from the exhaust path, then cooled by heat exchange with a low-temperature heat source of a heat pump, and afterward supplied indoors. Moreover, the air from the exhaust path is heated by heat exchange with the air from the intake path, then further heated by a heat source of the heat pump, and then divided into two branches. The air passing through one branched path is guided to the desiccant rotor and heats the first regeneration region to cause moisture retained by this first regeneration region to be released, thereby regenerating the moisture absorbing capacity of the desiccant rotor. The air passing through the other branched path is heated even further by the heat source of the heat pump, then guided to the desiccant rotor and regenerates the second regeneration region.